The present invention relates to a valve actuating mechanism.
It has been proposed in the prior art to interpose a lever between a fixed profile cam on a camshaft and a valve operated by the cam. By moving the pivot axis of the lever, it is possible to modify the valve lift.
The invention seeks to provide an improvement of such a valve actuating mechanism that permits not only the valve lift to be varied but also the event duration and phase while still using a camshaft having fixed profile cams.
According to the present invention, there is provided a valve actuating mechanism comprising a valve, a camshaft having a cam of fixed profile associated with the valve, a valve lifting rocking cam pivotable about a fixed axis and having a contoured surface that acts to open and close the valve as the rocking cam pivots about said fixed axis, and a cam following rocker comprising a cam follower in contact with the fixed profile cam on the camshaft and coupled to the rocking cam in order to cause the rocking cam to pivot about the fixed pivot axis with rotation of the camshaft, the rocker being pivotable about a second axis that is movable relative to the fixed pivot axis of the rocking cam in such a manner as to allow the valve lift, phase and duration of the valve event to be varied in dependence upon the position of the pivot axis of the rocker, characterised in that the rocking cam and rocker are pivotable about a cranked shaft that is rotatable about the same axis as the rocking cam, the rocker being mounted on an offset crank of the cranked shaft.